Antenna pattern tracer



Sept. 28; 1948.

M. L. JONES ANTENNA PATTERN TRACER Filed July 21, 1945 or a number of antennas.

Patented Sept. 28, 1948 UNITED STATES PATENT OFFICE 4 Claims.

The present invention relates generally to a device for computing or obtaining the radiation pattern of an array of antennas employed in directive broadcasting or the like. More particularly, the present invention aims to provide a simple and rugged mechanical apparatus which may be employed for obtaining or determining the radiation pattern of an array of any number of antennas in any desired arrangement.

Another object of the present invention is to provide a mechanical apparatus of the type described which may be readily built up with a series of duplicate assemblies, each assembly corresponding to an additional antenna.

A still further object of the present invention is to provide a mechanical apparatus as described which may be employed for determining the pattern of an array of a number of antennas and which provides for a simple adjustment to eliminate the elements that correspond to any one Thusby means of the present invention the apparatus may be set up to determine the pattern for, say five, antennas and the same apparatus may, by a, very simple adjustment be also made useful for an array of four, three, or two antennas.

These and other objects and advantages of the present invention will be apparent from the following specification and the accompanying drawings, in which:

Fig. 1 illustrates a proved embodiment of the present invention; and

Fig. 2 illustrates a radiation pattern of an array of antennas which may be obtained by the present apparatus.

When an array of antennas is installed for directive broadcasting or for any desired pur-' pose, the radiation pattern which is produced by the array is dependent upon four variables of each antenna. One pair of such variables comprises the spacing in degrees between adjacent antennas and the angle or orientation of each antenna with respect to the remainder of the array or with respect to a preselected reference line. Another pair of these variables includes the individual antenna current and its phase of each antenna.

In the present apparatus, which constitutes an embodiment of the present invention, a rotating arm constitutes the equivalent of each pair of variables indicated above.

When an array of two antennas is being treated or analyzed, one of these antennas may be said to be represented in the present apparatus by a fixed length and this length and the antenna to which it corresponds may be said to be the reference antenna; and only a single pair of rotating arms is employed, this pair representing the second antenna. It will now be understood that when we are concerned with an array of three antennas, a second pair of rotating arms is employed which will represent the four variables of the third antenna, and so on.

The present apparatus is intended to be employed by an electrical engineer who is in the process of designing or adjusting an array of antennas and the apparatus that are associated with such antennas. In designing such an installation the engineer needs to know the radiation pattern that will be produced by any arrangement of the antennas in the array, by any spatial arrangement of the antennas in the array and by any current and phase relationship of each of the antennas. By means of the present apparatus the engineer can make any series of assumptions for these four variables for each antenna and obtain a pictorial representation of the radiation pattern, all by the simple manipulation of the present apparatus and all in the course of perhaps a few minutes. Thus by the expenditure of very little time the engineer may obtain a large number of pictorial representations of a large number of radiation patterns which are produced by .a series of selected values for the four variables of each of the antennas. With these pattern-s before him, he may then make a proper selection of the arrangement of the antennas, their manner of operation, and also a design of the apparatus associated with such an array, depending upon the kind of use to which the array is going to be put.

Bearing in mind the above broad descriptio of the present apparatus, the point l0 may be said to constitute the mechanical equivalent of the first or reference antenna. Either of the additional antennas are represented in the present apparatus by the rotating arms H and I2. The drawing which is designed to illustrate the present invention as applied to an array having three antennas shows two sets of such rotating arms H and 12. This, however, is done merely for clarity and simplicity of exposition, it being understood that any number of such pairs of rotating arms H and I2 may be employed, depending upon the desired capacity of the machine.

Each of the arms II and I2 rotate over a dial bearing indications and degrees as indicated by the scale notations l3 and M. The zero point of the scales i3 and I4 is as indicated on the drawing, and the scales are graduated through 360 in 3 a clockwise direction therefrom. counterclockwise graduations may likewise be provided to facilitate readings in both directions, e. g., when adjusting the device by methods later to be described.

In order to permit the rotating arms I I and I 2 to correspond to variable quantities, means are provided for varying the effective length of each of these arms. Thi may be done by a variety of means Well known in the arts and in the present embodiment of the invention each arm is provided with a longitudinal slot indicated by the reference character I5 in the arm II and by the character IS in the arm l2. A pin, or a slider, or any other suitable element is disposed in each of these slots, is movable therealong, and may be fixed in any desired adjusted position. For this purpose the arms II and I2 carry suitable scales I! and I8, respectively; and the pin or slider or any other suitable element as indicated by the reference characters I9 and 20, respectively. It will be understood that the efiective length of each of the arms I I and I2 is determined by the position of the pins I9 and 20, respectively. In other words, the effective length of each of these arms corresponds to the distance from the axis of rotation of each arm to the pin I9 or 20, as the case may be. This is true because these pins, or sliders. or elements, I3 and 20, act, during the rotation of the arms II and I2, as cams upon elements associated with each of these arms which are thereby subjected to translational or lineal movement.

In the case of arm I I its rotation is transferred in the first instance to a single element for translational or linear movement thereof. In the case of arm I2 its rotation is transmitted to a pair of rectilinearly intersecting elements. Turning first to the arm II, the translational element associated therewith is represented by the bar 2I which is provided with a guide rod 22 disposed between any suitable number of guide pins 23. In the present apparatus as shown in the drawings, the bar 2I is. provided with a slot which engages the pin I9. It will now be understood that as arm II is rotated about its axis 25 it will subject the element which comprises the bar 2I and its guide rod 22 to translational or linear movement and this movement will have a cosine relationship to an angular movement of the arm II. It will be understood that any other desired means of transforming the rotational movement of the arm H into translational movement of the bar 2| and its rod 22 maybe employed.

The translational movement of the bar 2I and its guide rod 22 are again transformed into rotational movement of the arm I2. For this purpose the arm I2 is provided with a pulley or similar device 26 mounted at its fixed end. The diameter of the pulleys 2-6 is a matter of choice, whose magnitude depends on the desired angular movement of the arm l2. It is not necessary that the various pulleys 26 be of the same size. A string or cable 21, fixed at both ends on the bar 2I and the guide rod 22, is wound around the pulley 26 with the result that the translatory motion of the bar 2I is converted into rotational or angular motion of the arm I2.

The effective length of the arm II is made to correspond to the distance in space degrees of its antenna from the reference antenna, and the scale carried by the arm II corresponds to such distance. The angular position of the arm II corresponds to the orientation of its antenna.

Similarly, the position of the pin or slider 20 on the arm I2 determines its effective length and corresponds to the magnitude of the current oi field of the corresponding antenna and its angular position corresponds to the phase of that current or field. The slot [8 in the arm I2 will be seen to extend from the free end thereof to a point a little beyond the center of the pulley 26. This permits the pin 20 'to be adjusted to any position along the length of the slot including a position along the line of the axis of rotation of the pulley 26 and the arm I2. It will be understood that when the pin 20 is adjusted to this last position, namely, to the position where it lies along the axis of rotation of the arm and its pulley, the rotation of the arm will have no effect upon the apparatus. This adjustment is employed when it is desired to use the apparatus for analyzing an array consisting of a number of antennas less than the full capacity of the machine.

The rotating arm I I is adjustably fixed upon a rotating shaft 29 by means of the set screw 28. In the operation of the machine the shaft 29 is rotated manually or by any other desired means and the rotation of the arm I I is thereby transferred to the arm l2 in a cosine ratio. The present apparatus now provides mechanical means for continuously and automatically deriving the horizontal and vertical components of the rotation of the arm I2 and as will be understood later such components of the several arms I2 on the machine are summated or totalized and transferred to a summation apparatus. Turning first to the means for deriving the horizontal and vertical components of the rotation of arm I2; a pair of rectilinearly intersected bars 30 and 32 are provided as shown. These are provided with longitudinal slots 3I and 33, respectively, and the pin 20 carried by the arm I2 passes through the intersection of these slots. It will now be understood that as the arm I2 rotates the bar 30 will move vertically and therefore constitutes the vertical component of the rotation of the arm I2 and the bar 32 will move horizontally, thereby constituting the horizontal component of the movement of arm I2. The arm 30 is provided with a vertical guide rod 34 which moves between a series of guide pins 35. Similarly, the bar 32 is provided with a horizontal guide rod 36 which moves between suitable guide pins 31. The guide rod 34 is provided with a rotating pulley 52 at its free end, the guide rod 35 is provided with a rotating pulley 40.

It will now be understood that the structure thus far described may be duplicated any number of times depending upon the desired capacity of the apparatus. In the machine illustrated in Fig. 1, two such sets of rotating arms are shown together with the cooperating elements thus far described, bearing in mind that the rotating arms II are all mounted upon the shaft 29 and when fixed thereon in the desired position by means of the set screws 28 all such arms II will rotate and such rotation will be transferred to the corresponding arms I2 in the cosine ratio, and the rotation of each arm I2 will be automatically analyzed into their horizontal and vertical components, the horizontal component of the upper set of arms being taken up by the movement of the pulley l0 and its vertical component being taken up by the movement of the pulley 52. Another set of pulleys 40 and 52 are carried by the corresponding elements in the second set of rotating arms.

The summation device of the present apparatus includes a pair of rectilinearly intersecting bars 46 and 55, one being provided with a guide rod writing device is attached to the cable 58.

45 guided by a suitable set of guide pins 41, and the other being provided with a guide rod 54 operating between a suitable set of guide pins 4|. The bars 46 and 55 are slotted as shown and then a pin 56 passes through the slots at their intersection. A flexible cable 43 fixed at IU passes over the pulleys 40 and the intermediate pulleys 44 and is attached at its other end to the guide rod 45. It will now be understood that the horizontal movement of the bar 46 is the algebraic sum of the movement of all of the pulleys 4D and that it therefore is the algebraic sum of the horizontal components of movement of all of the arms I2. It will be seen that where there are more than two sets of rotating arms II and I2 the same flexible cable 43 is made to engage the additional pulleys 40.

Similarly, flexible cable 48 is fixed at point 49 and engages the pulleys 52 carried by the guide rods 34 and also passes over suitably fixed pulleys 5| and 53 and is attached at its free end to the rod 54. Tension springs 66 and 61 are employed in order to maintain the cables 43 and 48 in a tensioned condition.

The present apparatus also shows a means for indicating the magnitude at any instant of the vector sum of the horizontal and vertical components of intersecting bars 48 and 55, and for making a visible recording of the magnitude thereof as shaft 29 rotates. This apparatus comprises a cable 5-8 fixed at one end to the pin 5 the cable passing through the polished hole 59 in a fixed block 60 and fixed at point 6! through a retaining spring 62. The cable 58 may carry a pointer 63 which operates upon a dial 64. This particular form may be employed for taking reading instead of recording the pattern. In taking these readings the shaft 29 is first moved to any desired number of degrees and the reading of 63 on the scale 84 is recorded until a complete set of readings is obtained which may be plotted on coordinate paper later. A platform 65 is also provided which receives a sheet of polar coordinate paper and a pen 68 or any suitable The platform 65 is coupled to the shaft 29 to rotate therewith in a 1-to-1 ratio. The writing instrument 68 then produces on the paper on the platform 65 a representation of a pattern as shaft 29 rotates.

In setting up the machine the arms 12 are first adjusted to their zero positions by sliding the pins so that they coincide with the axis of rotation of the corresponding arms. It will be understood that with the pins 20 in this position the rotation of the arm l2 has no effect upon the bars which are associated with the arm, and the cables 43 and 48 are unaffected by such rotation. It is therefore proper to speak of the arms 12 as being adjusted to their zero positions when the pins 20 are disposed immediately along the line of the axis of rotation of the arms. With the arm l2 in their zero positions the bar 55 is adjusted to the position where its slot lies immediately under the polished hole 59. The cable 48 is then pulled taut and its end is fixed at 49. The cable 43 is adjusted in a similar manner. The bar 46 is adjusted to a position a predetermined distance from the polished hole 59, and which may be considered the unit of measurement employed in scale IS on the arms 12. Arms H and I2 may be calibrated in any convenient unit starting with zero, provided like arms are identically calibrated. The zero position for the arms H and I2 coincide with their axes of rotafor each set of arms II, I2.

6 tion. With the bar 46 held in this position the cable 43 is drawn taut and its free end fixed at the point J0. The displacement of the bar 46 with reference to the polished hOle 59 may be considered a reference vector of the system corresponding to th reference antenna.

The machine thus adjusted i now ready for use. Before the machine can actually be operated in order to determine the pattern of any particular array the arms ll, l2, have to be adjusted to positions that correspond to the several variables of the two remaining antennas. The effective lengths of the arms II are adjusted to correspond to the distance in degrees between the reference antenna and the antenna being adjusted.

For this purpose the bar ll may bear a cale which corresponds to the distance in degrees between antennas so that it would be sufficient to move the pin to such a position that it registers with the desired number of degrees. Such a construction and method of operation involves sources of error. It is preferred therefore in the present apparatus to employ a method of setting the arm l l which minimizes errors and eliminates the necessity for the scale.

As the first step in this adjustment the arm I! is first put in its QO-degree position. With the arm H in its QO-degree position set screw 28 is loosened and arm I2 is moved to its zerodegree position on its scale. Then set screw 28 is tightened and arm H is rotated to its zerodegree position, and permitting the arm 12 to assume its corresponding position. At this point the pin I9 is moved until the arm l2 points to the desired number of degrees on it scale. A similar series of operations are then performed All antennas are now properly adjusted as to the variable of degree spacing. The above method of adjustment is only necessary when because of mechanical imperfections in the apparatus, it is not possible to obtain accurate readings with the more simplified method of adjustment hereinafter outlined. This simpler method consists in first setting arms II and I2 at zero, with pin I 9 over its axis of rotation, and then moving the pin l9 until the arm [2 indicates a reading in degrees on the scale I4 corresponding to the distance in degrees between the reference antenna and the antenna represented by the arm I l. At this point one arm ll, fixed on its shaft, is held in its zero position and the adjacent arm II is moved on its shaft to indicate the desired orientation and is fixed on the shaft in this position. As a next operation, the arms l2 have to be adjusted for phasing. For this purpose the corresponding arm I l is set at degrees, which brings the corresponding arm I 2 to zero. The set screws 24 are then loosened and the arms I2 are moved to correspond with the degree of phasing, and the set screws are tightened.

As the last step in setting up the apparatus, the pins 20 are adjusted to a position against the scale shown on the arms which correspond to theratio of the current of the antenna with reference to the reference antenna.

The apparatus is now set and ready to compute or trace the pattern for the array of antennas. For this purpose a sheet of polar coordinated paper is employed to cooperate with the pen 68. The shaft 29 is slowly rotated one complete revolution, which produces a pattern on the sheet, one such pattern being illustrated in Fig. 2 only as an example. The table which supports the 7 sheet be 18 coupled to shaft 29 in a 1-to-1 ratio.

Fig. 1 shows a shaft 29 which carrie the two arms H and is designed to carry any other additional such arms as may be desired if an array containing more than three antennas is being analyzed. It will be understood, however, that the structure needs to be such that such arms H, etc., once adjusted to the desired positions subsequently rotate in unison.

Such unison rotation may be obtained by means other than a common shaft, such as by gears or belts and pulleys, or the like. Similarly, the employment of flexible cables 43 and 48 is shown for purposes of convenient illustration, it being understood that the transmission of movement between these various elements may be accomplished by other well-known means.

The machine as illustrated is designed for an array of three antennas. The same machine as constructed may be employed for obtaining the pattern of an array of two antennas. For this purpose a radial arm [2 is adjusted to its zero position, and when thus adjusted it has no effect upon the apparatus, and it may then be operated after the remaining arms H and I2 are properly adjusted for the two antennas array.

It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention i not limited by that which is shown in the drawing and described in the specification but only as indicated in the appended claims.

What is claimed is:

1. An apparatus for determining the pattern or field intensity of an array of a plurality of antennas, in which one of said antennas is a reference antenna, said apparatus comprising a pair of rotatable arms for each of the other antennas, the first of said arms carrying a slider movable longitudinally thereof and adjustable to a position corresponding to degrees of spacing of its antenna from the reference antenna, the second of said arms carrying an element movable therealong for an adjustment to a position corresponding to the current of the corresponding antenna, means interposed between said first and second arm for transmitting the rotation of the first to the second in a cosine ratio, a pair of intersecting bars associated with each of said second arms and movable with the said element when the arm is rotated, whereby the movement of one of said bars constitute the horizontal component and the the other the vertical component of the movement of said second arm a pair of intersecting summation bars, means mechanically connecting said summation bars with the first-named bars, whereby one of said summation bars moves a distance equal to the algebraic sum of the horizontal component of the movement of all said second arms and the other of said summation bars moves a distance equal to the algebraic sum of their vertical components, a slider carried by said summation bars at the point of intersection, and means for rotating said first arms in unison, the distance between the last-named slider and a fixed point thereby being made to correspond to the variations of the field intensity of the antenna array.

2. An apparatus for determining the pattern or field intensity of an array of a plurality of antennas, in which one of said antennas is a reference antenna, said apparatus comprising a pair of rotatable arms for each of the other antennas, the first of said arms having means for adjusting its efiective length in correspondence with the degrees of spacing of its antenna from the reference antenna, the second of said arms having means for adjusting its effective length in correspondence with the current of the corresponding antenna, means interposed between said first and second arms for transmitting the rotation of the first to the second in a cosine ratio, a pair of intersecting bars associated with each of said second arms and movable therewith when the arm is rotated, whereby the movement of one of said bars constitutes the horizontal component and the other the vertical component of the movement of said second arm, a pair of intersecting summation bars, means mechanically connecting said summation bars with the first-named bars, whereby one of said summation bars moves a distance equal to the algebraic Sum of the horizontal components of the movement of all said second arms and the other of said summation bars moves a distance equal to the algebraic sum of their vertical components, a slider carried by said summation bars at the point of intersection, and means for rotating said first arms in unison, the resultant movement of the slider thereby being made to correspond to the variations of field intensity of the array of antennas.

3. An apparatus for determining the pattern or field intensity of an array of a plurality of antennas, in which one of said antennas is a reference antenna, said apparatus comprising a pair of rotatable arms for each of the other antennas, each of said arms having means for adjusting its effective length, means interposed between said arms for transmitting the rotating of the first to the second in a cosine ratio, a pair of bars associated with each of said second arms and movable therewith when the arm is rotated, whereby the movement of one of said bars constitutes the horizontal component and the other the vertical component of the movement of said second arm, a pair of intersecting summation bars, means mechanically connectin said summation bars with the first-named bars, whereby one of said summation bars moves a distance equal to the algebraic sum of the horizontal components of the movement of said second arms and the other of said summation bars moves a distance equal to the algebraic sum of their vertical components, and means for rotating said first arms in unison, the resultant movement of the intersection of the summation bars thereby being made to correspond to variations of field intensity of the array of antennas.

4. An apparatus for determining the pattern or field intensity of an array of a plurality of an tennas, in which one of said antennas is a ref erence antenna, said apparatus comprising a pair of rotatable arms for each of the other antennas, each of said arms having means for adjusting its effective length, means interposed between said arms for transmitting the rotation of the first to the second in a cosine ratio, a pair of bars associated with each of said second arms and movable therewith when the arm is rotated, whereby the movement of one of said bars constitutes the horizontal component and the other the vertical component of the movement of said second arm, a pair of intersecting summation bars, means mechanically connecting said summation bars with the first-named bars, whereby one of said summation bars moves a distance equal to the algebraic sum of the horizontal components of the movement of said second arms MARTIN L. JONES.

REFERENCES CITED The following references are of record in the file of this patent:

10 UNITED STATES PATENTS Number Name Date 2,066,949 Ruiz Jan. 5, 1937 FOREIGN PATENTS Number Country Date 335,512 Italy Feb. 6, 1936 OTHER REFERENCES Proceedings of the I. R. E. May 1942, pages 233-237, article entitled A Mechanical Calculator for Directional Antenna Patterns.

Proceedings of the I. R. E. May 1942, pages 227-232, article entitled Horizontal-Polar-Pat- 15 tern Tracer for Directional Broadcast Antennas."

Article on pages 130 to 140 of Bell Laboratory Record for December 1937, entitled The Isograph-A Mechanical Root Finder. 

